Something along those lines seem plausible. I totally think there will be people who oppose the decision, and to that effect there will be some resistance, perhaps a group that wants to destroy the spirits.

I wonder if the avatar will be treated with less or more respect. On the one hand, she literally just saved the world a couple months after saving Republic City. On the other hand, she no longer has the guidance of past avatars and she made the very big decision to keep the portals open. She'll be held responsible for anything bad that happens between people and spirits, regardless of whether or not the decision was a good one overall.

I think she will be depended on to be a diplomat between the Spirits and the humans, even if she said that she won't be a "bridge between worlds", she's probably going to have to do some peace-making. A lot of spirits seem to hate humans and a lot of humans are probably going to hate spirits.

Here's the thing about the dark avatar. It would literally have to force itself on someone, unlike Raava who doesn't change your personality or physical shape. Vaatu would change a lot about you and I don't think anyone would become that. A bit of Fridge Horror for you.

I like this idea, but the next Dark Avatar reincarnation would still be a waterbender. Avatar Wan learned all the elements, thus creating the cycle. But the Dark Avatar only had water. Nothing connects it to the other elements.

I feel like the next book has to have a lot more Earth Kingdom in it since we haven't been there in LoK yet. I would be interested to see if the Dark Avatar would get reincarnated like the regular Avatar does. If that follows the cycle of the elements as well, the next Dark Avatar would be from the Earth Kingdom. Imagine if they identified a child as the literal embodiment of darkness and had to decide what to do with him. What if it was the Earth King/Queen's son? That could cause some serious political shit.

Season 1 was a quick wrap-up of the loose ends, but because of that, season 2 barely even referenced the events of season 1.

With the end of season 2 though, it leaves a lot of plot lines to carry on. Now the spirit portals are open, spirit-human wars will be a possibility. I expect there will be human tour groups to the spirit world, and that will disrupt everything and the spirits will get angry...etc. There's the big mystery of whether Korra can reconnect to her past lives, a proper explanation of Jinora and all the loose ends surrounding the finale..etc.

So, next season may be a different story, but the transition and continuity isn't so broken and abrupt.

This did tie up fairly well, but there is the matter of Verick escaping, and things did change a lot with the spirit world, and then there's Jinora being somehow awesome with spirits (which I think they should definitely explore/explain), and then there could be something with Vaatu returning from within Korra/Raava.
It isn't like TAS was with the overarching Fire Nation threat, but this will carry over better than season 1 did at least.

I think it's interesting how Legend of Korra differs from The Last Airbender in that the seasons have tied up really nicely so far. The first season had an excuse because the creators didn't know if the show would continue, but even this season tied up pretty nicely. In TLA, there was always an overarching story that tied everything together (it was all about the Fire Nation taking over). With Korra, I wonder if every season will be more or less separate. But there is Verick. He's still out there someplace, so I guess that will carry over.

I'm just hoping they wait a few books before having a reincarnation of the Dark Avatar being revealed as behind everything. He/she wouldn't have the 4 elements to bend, maybe just 1 at best, so he/she would have to step pretty carefully, work behind the scenes trying to bring the whole world down around the avatar's ears.... I'm thinking like Sauron in the simirilian style manipulation of countries.... Man that'd be cool.

I was hoping the Vaatu/human combination would involve something other than bending. I'd be interested if he/she could do more interesting spirit-y stuff. It'd be great if they made a whole different system for the Dark Avatar unrelated to bending. Because I was thinking the whole time "what really makes the Dark Avatar different from the regular one? It's got tentacles and a belly beam, and it can't bend 4 elements. It's like a Power Ranger enemy. I am dissapoint."

I kinda like that he'd definitely lose to the avatar in a heads up fight, we establish that now so that when the dark avatar reincarnates he/she has a reason to be sneaky evil instead of picking a fight.